A secret can be told only 2 persons in 5 mins, the same person tells to 2 more persons and so on.In how many minutes will it reach 768 persons?

• Ans : 45 minutes.
  
  This will form a binary tree. so the maximum numbers of nodes that can be formed by the tree is 2^(d+1) - 1 . where d is the depth of the tree.
  So, the number 768 will come when d will be 9. That means (2^8+1 - 1) < 768 < (2^9+1 -1).
  One depth takes 5 minutes. So, 9 depth will take 9 * 5 = 45 minutes.
  
• 8 years agoHelpfull: Yes(5) No(7)
• 47.5 minute
  its like as 1,2,4,8,.....,256 the time taken as 45 min here and 2.5 min to take remaning person
  so total answer is 47.5 min
• 8 years agoHelpfull: Yes(5) No(0)
• IN FIRST 5 MINUTE THE SECRET WILL SPREAD TO 3 PERSONS. IN NEXT 5 MINS IT'LL SPREAD TO 6 PERSONS...SIMILARLY 3,6,12,24,48,96,......IT TAKES 45 MINS OVERALL
  
• 8 years agoHelpfull: Yes(4) No(2)
• 50 as it becomes expanding to the power two till 10
• 8 years agoHelpfull: Yes(2) No(2)
• Ans: 50minutes
  
  2=5min ->2person
  2^2=10 min ->4person
  2^3=15min ->8 person
  2^4=20min ->16 person
  2^5=25min ->32person
  2^6=30min ->64 person
  2^7=35min ->128person
  2^8=40min ->256 person
  2^9=45min ->512person
  2^10=50min ->1024person
  secret has to be conveyed to 768 persons it is b/w 512 and 1024 hence required is 50minutes.
  
  
• 8 years agoHelpfull: Yes(1) No(3)
• ans 47.30s
• 8 years agoHelpfull: Yes(1) No(3)
• for 1 person to 2 its 5 minutes.,
  next 2 will tell two other two two.
  so this order follows.
  1+2+4+8+16+32+64+128+256=40 mins and rest 257 shoud take half of the 5 mints to tell the secret . so answer is 42.5 mints
• 8 years agoHelpfull: Yes(1) No(0)
• ANS: 50 because A binary tree has child 2^h-1=max no. of nods(768) where h= height of binary tree ,
  solution :
  2^9=512 ....... 9*5=45min
  2^10=1024....... 10*5=50min
  from 513 to 1024 it will take only 5 extra min
  so 45+5=50
• 8 years agoHelpfull: Yes(1) No(0)
• person called in 5/2 min=2.5 min
  then 768 person2.5*768=1920 min
  32 hours
• 8 years agoHelpfull: Yes(0) No(1)
• Ans 50min.
  2^1=2=5min
  2^2=4=10min
  
  
  2^9=512
  2^10=1024
  10*5=50
• 8 years agoHelpfull: Yes(0) No(1)
• ans : 47 min 5 sec
• 8 years agoHelpfull: Yes(0) No(0)
• i agree with Mr.anantatdas
  but the calculation at the 9th level is wrong.
  it takes (no. of nodes in the level*5mins per pair).
  Hence , the answer is 1820 mins.
• 8 years agoHelpfull: Yes(0) No(0)
• 45 min ...
  
• 8 years agoHelpfull: Yes(0) No(0)
• 2^x = 768
  
  x = log(768) / log(2)
  
  x = 9.5849
  
  Then times that by the doubling time = 5 minutes
  
  9.5849 * 5 = 47.9245 minutes = 47 minutes, 55.47 seconds
• 8 years agoHelpfull: Yes(0) No(0)
• 47.5 is correct answer
• 8 years agoHelpfull: Yes(0) No(0)
• The ans is 47.5 mins
• 8 years agoHelpfull: Yes(0) No(0)